The first "air drop" was made on the Mendenhall Fire,
August 12, 1955, on the Mendocino National Forest. The first operational air tanker was developed in Willows, by the Willows Flying Service in 1955, at the request of the Fire Control Officer for
the Mendocino National Forest. A Boeing Stearman 75 "Caydet"
Agricultural Aircraft was modified with a 170 gallon tank
at the Willows airport. This Aircraft, N75081, became the first registered free fall air tanker in the history of aviation.
In 1956, seven agricultural aircraft were modified and formed
the first operational air tanker squadron in the United States.
Piloted by local aviators, this squadron operated out of the Willows Airport
fighting wildfires throughout California. Initially, plain water was used as the fire suppressant. However, it was soon discovered that most of the water evaporated before reaching
the fire, so the practice was adopted of adding chemicals
to the water to inhibit evaporation.
Borate was one of the first chemicals used, hence the derivation
of the term "borate bomber."
In 1959, heavy air tankers, capable of carrying 2,000 gallons
of fire retardant, were providing an effective tool in controlling
.........Enter the A-26 Invader
Ever since N5457V, the first A-26 converted to a fire tanker
by Aero Atlas back in 1959, this highly manoeuvrable, single pilot, Ex-WWII attack aircraft has proven its worth in the
wildfire theatre of operations, due to its speed, flight duration ( 5 Hours ), Range (1,200 Miles ) and ability
to carry a good fire retardent load of 760 US gallons, the A-26 Invader became the mainstay in the battle to deal with the
ever growing problem of forrest fires in both Canada and the United States, with some 50-60 A-26 Invader's being converted
for Air tanker or drop planes of some or other description, culminating in the ultimate A-26 Air tankers operated by Lynch
and modified with STOL capability.
And to prove the durability of the A-26, N5457V as mentioned above still
flies today, owned and operated by David R. Lane.
The first Invaders used for Air Tanker duties comprised of modifications
consisting of systems and componants from a variety of othe aircraft of that era.
The basic conversion consisted of installing an aluminum tank
with two internal compartments, each having the capacity of 500 + gallons of slurry and their own doors in the bombay, an
electrically powered hydraulic system, which was the tail turret hydraulic system removed from a PB4Y-2 and the associated
wiring, tubing and controls to operate the tank doors.
In most of the aircraft, the hydraulic panel was located on the
starboard side of the cockpit, with the jumpseat removed and which was eventually replaced with a lap belt so a passenger
could be carried when required. Just aft of the mainspar, a 1 ft x 3 ft rectangular hole was cut on top of the fuselage for
The windbreaking strakes which were mounted just forward of the bombay were removed and in most cases, the opening was not covered. The tanks fitted
snuggly in the bombay and extended 2 or 3 inches below the bombay.
The most noticable difference was in the bottom of the tank.
On some tanks, the bottom was flat from side to side, while on
others the center line of the tank would be 3 or 4 inches lower than the sides creating a splayed V when viewed from the front.
The list below gives just some of the companies that used
the A/B-26 for various Air Tanker and Agricultural spraying duties.
Photos for several of the companies are not available, so a brief
history has been inserted whilst a suitable image can be located.
For history and data on individual Invaders throughout the
site, I would like to credit the Warbirds Worldwide Directory by John Chapman, thank you John.
How it works
Tankers are used to flank or work parts of a fire to contain
it's direction or slow it's rate of spread while ground troops work the fire.
Retardant lines may be used to reduce rate of spread or
encourage the fire to move in another direction based on wind, natural barriers, vegetation or types of fuels, topography,
slope, aspect (north/south, etc), and of course, threats to persons, structures, etc. Considerations include resources available
to back up retardant lines, ground resources, turnaround times, etc.
One of the single most common, and most basic
mistakes in retardant application, is to attack the head of the fire, or to go direct on the fire. Without an ability to build
line rapidly with short turn-around times or ample air assets, the result is invariably splitting the head of the fire into
two or more parts, increasing the rate of spread, and complicating the fire. Most of the time, this only increases fire activity,
wastes retardant, and makes the fire worse.
Water cools fire directly, but cooling the fire is the least effective
way, and most wasteful way, of controlling it's activity. Unless it's a small spot fire, then water doesn't put the fire out.
Water and foam are short term measures, often most effectively used on small spot fires. Where water can be used in extended
attack operations, it has to be available in very large quantities, and enough resources need to be present and capable of
acting, which can keep a constant application of water on the fire. Scoopers, for example, must have the ability based on
proximity of an uplift source, a short distance, and enough scoopers, to keep putting water on the fire every few minutes.
Otherwise, the water is usually nearly worthless.
One must remember that in an active wildfire, temperatures above
the fuels can exceed two thousand degrees Farenheight, and fuel temperatures and fire activity can mean that water dropped
on an active flame front may do little more good than spitting in a camp fire. Water evaporates quickly, any cooling or loss
of energy in the fire is quickly replaced and reheated, and the change in relative humidity is so minute that it's negligible
Relative humidity of it's own accord does reduce fire behavior somewhat in intensity and rate of spread,
but is a minor consideration compared to winds, slope, fuel moisture, etc.
Fuels on the ground are classed by the amount
of hours required to effect a change in fuel moisture. Some fuels such as grass are one-hour fuels, but many fuels over 3"
in diameter, like small tree branches, are into the thousand hour range. The introduction of local temporary changes in RH
produce insignificant changes in the fire behavior for the most part, and no changes in the fuel moisture. Even a rainstorm
only produces brief changes, and doesn't effect fuel moistures save for grasses and other one-hour fuels; the result in controlling
fire spread isn't great.
Fire won't "back off" by dropping scooping aircraft and helo buckets nearby. Nor do ground
troops wait for a fire to "back off." Air assets are tools that ground troops request or use to apply to specific parts of
a fire, in order to assist them in working the fire. Ground troops often work the fireline directly with shovels, pulaski's,
handlines (hoses and water or foam), lighting backfires or backburns, running dozer or cat lines to cut away fuels and create
fire breaks, and other tactical methods of fighting fires. In accomplishing this mission, they may request a helicopter to
put water on a hotspot or to work a segment of a flank. They may look for a retardant drop to back up a bulldozer line or
a road, to prevent spread across the road. In each case, the retardant use or water use is only one tool of many that the
ground troops have at their disposal when working the fire.
Initial Attack planes are often the first one on scene,
and in some cases, do end up working the entire fire from the air. These efforts are always considered a temporary measure,
buying time for a helattack team or hotshots to come in and hit the tree with a chain saw, dig a line around it, or do whatever
is necessary to actually control and put out the fire.
Often as not, the most effective means of putting out a fire
is to supervise it burning itself out. Air assets are put in use to attempt to reduce damage to danger to structures of personnel
until that happens. A lot of fires are far beyond the capability of man to control, or extinguish, and firefighting efforts,
both in the air and on the ground, are futile motions that take place in earnest, until nature decides enough is enough.
air tankers are one tool in the toolbox...but only one. You need not only the aircraft, but enough bases capable of supporting
them, close enough to fires, spread throughout the country, to do some good. The result was that the fire burned over our
line before we could load and return with more retardant, and we were effectively wasting our time. The State of Florida wanted
us to keep dropping however, because often as not it's as much a matter of public relations as it is doing anything effective.
It was a given that we couldn't control the fire, but it was important that the public felt like every effort was being made
to do so.
grounding: In the United States, most of these
aircraft are privately owned and contracted to government agencies, and the National Guard and the U.S. Marines also maintain
fleets of firefighting aircraft. On May 10, 2004, The U.S. Forest Service (USFS) and the Bureau of Land Management (BLM) suddenly
announced that they were cancelling contracts with operators of 33 heavy airtankers. They cited liability concerns and an
inability to safely manage the fleet after the crashes of a C-130A Hercules in California and a PB4Y-2 in Colorado during
the summer of 2002. Both aged aircraft broke up in flight due to catastrophic fatigue cracks at the wing roots, so sadly as
a result of the new legislation no A-26's currently fly in an air tanker capacity.